A person who is so hideously ugly and/or disgusting that to consider intercourse with them you would require a bag over their head, one for yourself just in case their's falls off, and one for your dog...yeah you're that embarassed.

Ol' Bruce is such a triple bagger that even Janie, the cum dumpster that she is, wouldn't touch him.

anyone (male or female) who is so hideous that before you even thought of losing your dignity to that extend you'd need three bags: one for their head, one for yours in case theirs came off, and one to be sick in after.

'what happened to you, you look dreadful'
'if you must know, I woke up next to a triple-bagger, ok'